1. Technical Field
The invention relates to vehicle suspensions. In one aspect, the invention relates to a trailing beam suspension for a wheeled vehicle in which the suspension includes a mechanism for fore or aft adjustment of the alignment of the axle and wheels with respect to the longitudinal axis of the vehicle.
2. Related Art
Proper wheel alignment in road vehicles is important to prevent undue tire wear. Common causes of improper wheel alignment include improper initial suspension system installation, accident damage, and impact or shock loads imposed on suspension components by potholes or other irregularities in the road.
Wheel alignment adjustment mechanisms permit adjustment of the alignment of vehicle axles and wheels with respect to the vehicle frame. Adjustment mechanisms are generally one of two types: (1) those that are adjustable as the suspension is installed on the vehicle and then permanently fixed in the adjusted position by welding or the like, and (2) those that are adjustable any time during and after installation and are held in the adjusted position mechanically.
U.S. Pat. No. 3,960,388 to Strader et al., which is incorporated herein in its entirety by reference, is an example of the first category of alignment devices. The Strader '388 patent discloses a trailing beam suspension that incorporates a mounting plate for the trailing beam having a pair of bosses that engage slots in the hanger bracket. The trailing beam is attached to the hanger bracket by a bolted connection in which the bolt passes through the mounting plate and is secured with a nut. The bolt head engages the mounting plate so that rotating the bolt pivots the mounting plate about one of the bosses. Pivoting of the mounting plate moves the bolt fore or aft, which moves the trailing beam fore or aft to align the axle. When the axle and wheels have been properly aligned, the plate is welded to the hanger bracket. Further adjustment is possible only after removing the weld.
U.S. Pat. No. Re. 30,308 to Masser discloses a trailing beam suspension system incorporating a mounting plate for the trailing beam having a single boss that engages a slot in the hanger bracket. The pivot bolt for the trailing beam passes through the mounting plate and slot. The trailing beam is moved fore or aft until proper alignment of the axle and wheels is achieved. The mounting plate is then welded to the hanger bracket. Further adjustment is possible only after removing the weld.
U.S. Pat. No. 4,991,872 to Richardson discloses a trailing beam suspension for a low-bed trailer. The forward trailing beam of a pair of trailing beams is mounted to the intermediate, inclined portion of the trailer's main structural beam through a bushing assembly. The bushing assembly is held to the web of the beam by a bolted connection. The web is provided with slotted mounting holes that enable adjustment of the alignment of the trailing beam and attached axle. The trailing beam is moved fore or aft until the axle and wheels are properly aligned. After adjustment, the bushing assembly is welded to the beam. Further adjustment requires removal of the weld and loosening of four bolts connecting the bushing assembly to the trailer beam.
An example of the second category of alignment devices is disclosed in U.S. Pat. No. 5,201,898 to Pierce. The Pierce '898 patent discloses a trailing beam suspension incorporating a pair of complementary discs that engage each other with a channel and rib arrangement, with the trailing beam mounting bolt passing therethrough. One disc is welded to the hanger bracket and incorporates an asymmetrical hole. The second disc contains an off-center hole and is rotatable relative to the first. The rotation of the second disc relative to the first is translated into lateral movement of the trailing beam mounting bolt. It is necessary to restrain the second disc against further rotation while the connection is tightened to prevent movement of the trailing beam from its aligned position.